In many telecommunication systems, communications networks are used to exchange messages among several cooperating spatially-separated devices. The various types of networks may be classified in different aspects. In one example, the geographic extent of the network could be over a wide area, a metropolitan area, a local area, or a personal area, and the corresponding networks would be designated as wide area network (WAN), metropolitan area network (MAN), local area network (LAN), or personal area network (PAN). Networks may also be distinguished by the switching or routing technique used to interconnect the various network nodes and devices (e.g. circuit switching vs. packet switching), by the type of physical media employed for transmission (e.g. wired vs. wireless), or by the communication protocols used (e.g. Internet protocol suite, SONET (Synchronous Optical Networking), Ethernet, etc.).
One important attribute of communications networks is the usage of wired or wireless media for the transmission of electrical signals among the constituents of the network. In the case of wired networks, tangible physical media such as copper wire, coaxial cable, fiber optic cable, etc. are employed to propagate guided electromagnetic waveforms which carry message traffic over a distance. Wired networks are more static forms of communications networks and may be favored for interconnection of fixed network elements or for bulk data transfer. For example, fiber optic cables are often the preferred transmission media for very high throughput transport applications over long distances between large network hubs, such as, bulk data transport across or between continents over the Earth's surface.